This invention relates to compliant pads for electrical devices and more particularly to compliant pads capable of accommodating the movement of devices and of accommodating the plurality of devices exhibiting different sizes.
Portable electronic devices such as radios typically use an energy storage medium (battery) to derive power necessary for operation. A battery can comprise a single battery cell or a plurality of battery cells arranged in a stick fashion, end-to-end, for example. A contacting scheme is required to reliably connect the energy source with the external electronic circuitry in the electronic device during all modes of operation.
An example of a more demanding mode is when the electronic device such as a radio has been dropped. Any movement of the battery during the shock and vibration created by the impact of the drop that causes a loss of power (a physical battery connection is broken) will cause unpredictable device operation, or in a case of a device with volatile memory circuits, a total loss of the memory's contents. An important point which must be considered in the case of portable communications devices, such as radios, is that the mass of the battery is a majority of the total mass of the electronic device. This creates problems in the design of a system to effectively retain the battery in a constant position during operation in all possible orientations and modes.
Batteries are often cylindrically or rectangularly shaped and include positive and negative electrical contact surfaces at their opposed ends respectively. Consequently, the battery is generally located in a cylindrical chamber or a rectangular chamber formed within a battery housing. To contact a battery, present embodiments require that conductive contacts be placed at opposite ends of the cylindrical or rectangular chamber so as to electrically and mechanically contact the respective positive and negative battery terminal surfaces of the battery situated in the chamber. Using conventional spring contacting methods, a conductive spring that compresses when the battery is inserted is situated at one end of the chamber. The spring force exerted by the contact acts to retain the battery against an opposing contact which is typically located on the opposite end of the battery.
For the production of battery packs, where the cells are placed end-to-end, intercell connections such as welds are often used between cells to prevent the plurality of battery cells from being permanently dislocated or displaced due to a vibration or a drop of the electronic device. The intercell connections are necessary since typically the contact spring force of the spring contact at the end of the cell string is not high enough to overcome the high frictional forces required to eliminate the internal rattle of the cells during vibration or a drop.
However, the design objective for an optimal contacting scheme generally dictates that the number of contact interfaces should be minimized. Following this objective will give a design with improved reliability as compared with a design having more interfaces. For example, if the intercell connections are eliminated, improved reliability will result. In addition, manufacturing cycle time will be reduced with the eliminated step to spot weld battery cells together in a battery pack. Thus, what is needed is a means for reliably contacting an energy source used to power an electronic device during all modes of operation.